New designs of 2-D Lead iodide perovskites
Sudeep Maheshwari a, Nicolas Renaud a, Tom Savenije a, Ferdinand Grozema a
a Delft University of Technology, The Netherlands, Julianalaan, 136, Delft, Netherlands
nanoGe Perovskite Conferences
Proceedings of Perovskite Thin Film Photovoltaics (ABXPV17)
València, Spain, 2017 March 1st - 2nd
Organizers: Henk Bolink and David Cahen
Poster, Sudeep Maheshwari, 094
Publication date: 18th December 2016

2D derivatives of hybrid halide perovskites are currently receiving increasing attention not only for their applications in photo-voltaics but also in other fields for their characteristic high photoluminescence and color tunability. The hydrophobic long chain cations act as an asset for their higher stability. The low dimensionality of the inorganic layer in 2D perovskites leads to quantum confinement effects and thus high exciton binding energy. Also, the low dielectric constant of organic cations leads to lower screening and thus lesser separation of charges. In this study we have tried to design new 2D perovskites by substituting the long organic cations with highly electron deficient cations targeting charge separation. We have performed DFT and TD-DFT calculations with lead-iodide inorganic layers coupled with electron-deficient naphthalene diimide dibutylammonium (NDI-dbu), and perylene diimide dibutylammonium (PDI-dbu)) cations. Subsequently the cations were substituted with electron donating and withdrawing groups. Through this study we demonstrate the effects of electron deficient linker groups in between the inorganic layers on the electronic structure of the 2D perovskites. Our study shows that the electron deficient organic cations have low-lying electronic levels and thus lead to small band gap. The pi-conjugated core of the organic molecules dominates the energy states of the conduction band whereas the covalently linked inorganic layer dominates the valence band. This has implications on the charge mobility of electrons and holes. The substitution of the electron donating groups at the bay area leads to an increase in the band gap of the material. With higher conjugation in the organic cation, the effective masses in the perovskite layer tend to decrease. We have also looked into the absorption properties of these materials and found increased absorption for higher conjugated organic cations.



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